26. (B)lack holes __________ not be seen directly, so determining the number of them is a tough task. (A). can (B). should (C). must (D). need

25.II. Grammar and Vocabulary (D)irections: (B)eneath each of the following sentences there are four choices marked (A), (B), (C) and (D). (C)hoose the one answer that best completes the sentence. --- It’s a top secret. --- Yes, I see. I will keep the secret __________ you and me. (A). with (B). around (C). among (D). between